diff --git a/include/event2/event.h b/include/event2/event.h
index 82015365..e9fad7bb 100644
--- a/include/event2/event.h
+++ b/include/event2/event.h
@@ -608,6 +608,9 @@ void event_base_free(struct event_base *);
 
 /**
    As event_free, but do not run finalizers.
+
+   THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
+   BECOMES STABLE.
  */
 void event_base_free_nofinalize(struct event_base *);
 
@@ -845,6 +848,9 @@ int event_base_got_break(struct event_base *);
  * To use this option safely, you may need to use event_finalize() or
  * event_free_finalize() in order to safely tear down an event in a
  * multithreaded application.  See those functions for more information.
+ *
+ * THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
+ * BECOMES STABLE.
  **/
 #define EV_FINALIZE     0x40
 /**@}*/
@@ -1016,7 +1022,11 @@ int event_assign(struct event *, struct event_base *, evutil_socket_t, short, ev
 void event_free(struct event *);
 
 /**
-   Callback type for event_finalize and event_free_finalize().
+ * Callback type for event_finalize and event_free_finalize().
+ *
+ * THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
+ * BECOMES STABLE.
+ *
  **/
 typedef void (*event_finalize_callback_fn)(struct event *, void *);
 /**
@@ -1047,6 +1057,9 @@ typedef void (*event_finalize_callback_fn)(struct event *, void *);
    add events, activate events, or attempt to "resucitate" the event being
    finalized in any way.
 
+   THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
+   BECOMES STABLE.
+
    @return 0 on succes, -1 on failure.
  */
 /**@{*/
@@ -1131,12 +1144,18 @@ int event_del(struct event *);
    As event_del(), but never blocks while the event's callback is running
    in another thread, even if the event was constructed without the
    EV_FINALIZE flag.
+
+   THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
+   BECOMES STABLE.
  */
 int event_del_noblock(struct event *ev);
 /**
    As event_del(), but always blocks while the event's callback is running
    in another thread, even if the event was constructed with the
    EV_FINALIZE flag.
+
+   THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
+   BECOMES STABLE.
  */
 int event_del_block(struct event *ev);